As a material for forming in advance an adhesive layer on a bonding object surface of a bonding object in order to fix a rubber layer onto the bonding surface, in Patent Literature 1, there is a disclosure of an adhesion sheet. In bonding of the rubber layer onto a metal, the adhesion sheet functions as an adhesive between a surface of the metal serving as the bonding object and an unvulcanized rubber layer to be bonded onto the surface of the metal. First, the adhesion sheet is described.
In FIG. 9, a film 20 of the adhesion sheet disclosed in Patent Literature 1 is illustrated. An adhesion sheet 20 disclosed in Patent Literature 1 includes a film 21, a top coating adhesive layer 22, and an undercoating adhesive layer 23. The film 21 of the adhesion sheet 20 is paper or the like, or a sheet material made of, for example, a polymer compound, specifically nylon, polypropylene (PP), polyethylene (PE), polyester, or polyimide. As a material for the film, a material having high heat resistance is preferred, and hence a film whose material is a polymer compound having high heat resistance, such as polyester or polyimide, is preferred. Of the polyesters, polyethylene terephthalate (PET) or the like is said to be most suitable as the material for the film.
A “solvent-dispersed vulcanized adhesive” having reactivity to the rubber layer to be bonded is applied onto a surface of the film 21 on one side. For example, under a state in which the film can be continuously fed, the solvent-dispersed vulcanized adhesive is applied onto the surface of the film on one side and formed. The solvent-dispersed vulcanized adhesive is formed into the top coating adhesive layer 22 to be finally formed. After the application, the adhesive is dried by evaporating a solvent that is a volatile component. Thus, the top coating adhesive layer 22 of the solvent-dispersed vulcanized adhesive is formed on the surface of the film 21 one side. The top coating adhesive layer 22 serves as a rubber layer-side adhesive when the rubber layer is bonded onto a metal.
After the formation of the top coating adhesive layer 22 on the surface of the film 21, the undercoating adhesive layer 23 is further formed on a surface of the top coating adhesive layer 22 on an upper side (surface on the opposite side to the film 21 out of the surfaces of the top coating adhesive layer 22). The undercoating adhesive layer 23 is formed by applying an adhesive having reactivity to the metal serving as the bonding object. The undercoating adhesive layer 23 is formed in the same manner as in the case of the formation of the top coating adhesive layer 22. For example, the film 21 having formed thereon the top coating adhesive layer 22 is continuously fed from a roller at a constant speed, and the adhesive is applied onto the surface of the top coating adhesive layer 22 of the film 21 at a predetermined thickness. After the application, the adhesive is dried so as to evaporate a solvent that is a volatile component. As a result, the adhesive sheet 20 in which the top coating adhesive layer 21 of the solvent-dispersed vulcanized adhesive is formed on the surface of the film 21 on one side and the undercoating adhesive layer 23 is further formed thereon is obtained. When the rubber layer is bonded onto a metal, the top coating adhesive layer 22 serves as a metal-side adhesive. The undercoating adhesive layer 23 is interposed between the rubber layer and the bonding object, and the adhesive layers allow the unvulcanized rubber to be fixed onto the bonding object.